Fuel cells generate electricity by a chemical reaction wherein oxygen gas is reduced to oxygen ions (O2−) at a cathode, and a fuel gas, such as H2 gas, is oxidized with the oxygen ions to form water at an anode. Solid oxide fuel cells employ a hard, ceramic compound metal (e.g., calcium or zirconium) oxide as an electrolyte between a functioning cathode and a functioning anode.
In some embodiments, fuel cells are arranged in stacks, whereby subassemblies, each including a cathode, an anode and a solid electrolyte between the cathode and anode, are assembled in series by locating an electrical interconnect between the cathode of one subassembly and the anode of another. However, fabrication of fuel cells and stacks can be susceptible to damage caused by a fluctuation in temperature. Rapid changes in temperature also can affect the life of fuel cells as a consequence of differences in coefficients of thermal expansion among the materials that make up the cathode, electrolyte, anode and interconnect components. Moreover, some components of fuel cell subunits, such as porous layers, including active cathode functional layers of fuel cell subunits, preferably are exposed to lower temperatures during fabrication than generally are required for the remainder of each fuel cell subunit. All of these problems are compounded by assembling fuel cell subunits in stacks which must be co-fired during production, and by extended use of stacked assemblies which may be exposed to repetitive and dramatic changes in temperatures during normal operation.
Therefore, a need exists to minimize or eliminate the above mentioned problems.